Method of determining modulation order and transport block size in downlink data channel, and apparatus thereof

ABSTRACT

The present disclosure relates to a method and apparatus for configuring a resource for the transmission/reception of data. More particularly, the present disclosure relates to a method and apparatus for configuring an MCS and a TBS for an MTC terminal. Particularly, provided is a method and apparatus for determining a TBS by an MTC terminal. The method may include receiving scheduling information transmitted based on an MCS used for the MTC terminal and a TBS table and determining a TBS using the scheduling information provided by a base station.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority from Korean Patent Application Nos.10-2015-0155867, filed on Nov. 6, 2015, Korean Patent Application No.10-2016-0027603, filed on Mar. 8, 2016, which are hereby incorporated byreference for all purposes as if fully set forth herein.

BACKGROUND 1. Field of the disclosure

The present disclosure relates to a method and apparatus for configuringa resource for the transmission/reception of data. More particularly,the present disclosure relates to a method and apparatus for configuringan MCS and a TBS for an MTC terminal.

2. Description of the Prior Art

Modulation refers to transforming signal information (e.g., intensity,displacement, frequency, or phase) into an appropriate waveform to beappropriate for channel property of a transmission medium. In addition,digital modulation refers to transforming a digital signal (that is, adigital symbol stream) into a signal that is appropriate for a channelproperty. Such a digital signal transmits digital information bymatching the same to one of various available signals (a signal set). Asa representative digital modulation scheme that has high bandwidthefficiency, a M-ary QAM modulation scheme expressed in 2^(M)QAM, suchas, QPSK(or 4QAM), 16QAM, and 64QAM are used.

Modulation methods used for downlink data transmission in a wirelesscommunication system (e.g., long term evolution (LTE) or LTE-Advanced)are QPSK, 16QAM and 64QAM. Through the modulation methods, a basestation transmits data to a terminal, and the terminal demodulates thetransmitted signal so as to receive the data.

The base station selects one of the modulation methods based on adownlink channel state and reports the same to the terminal usingdownlink control information (DCI). The terminal determines the receivedDCI and executes demodulation that is appropriate for a data modulationscheme so as to receive the data.

To this end, the terminal measures the downlink channel state andtransmits information on the measured channel state to the base station.Also, the base station determines modulation and coding scheme (MCS)index information that is mapped to each of QPSK, 16QAM, and 64QAM basedon the information associated with the channel state and determines atransport block size (TBS).

In this instance, it may be inefficient to determine a modulation methodand a TBS in the same manner as described above and to configure DCIeven when a terminal uses a low data transmission rate based on channelproperty of the terminal that uses an LTE network.

Therefore, a modulation method and a TBS need to be set to be differentbased on channel property of a terminal. Also, there is a desire for anew scheme for configuring DCI based on a modulation method and a TBS,which are set to be different, and enabling a terminal to determine thesame.

SUMMARY

In this background, an aspect of the present disclosure is to provide amethod and apparatus for determining a modulation method and a transportblock size (TBS), which are used when a downlink data channel istransmitted to a terminal that uses a low data transmission rate amongterminals that use an LTE network.

Also, another aspect of the present disclosure is to provide a methodand apparatus for configuring downlink control information using amodulation method and a TBS, which are set to be different based on thechannel property of a terminal, and is also for determining, by theterminal, the modulation method and the TBS in the downlink data channelbased on the same.

In accordance with an aspect of the present disclosure, there isprovided a method of determining, by a terminal, a modulation order anda transport block size (TBS) in a downlink data channel. The method mayinclude: receiving, from a base station, downlink control information;determining the modulation order used in the downlink data channel usingi) a modulation and coding scheme (MCS) table having at least one of TBSindices set to be identical to MCS indices and ii) an MCS index includedin the downlink control information; and determining a TBS index usingthe MCS table and the MCS index included in the downlink controlinformation, and determining a TBS in the downlink data channel using aTBS table including TBS indices and the determined TBS index.

In accordance with another aspect of the present disclosure, there isprovided a method of determining, by a base station, a modulation orderand a transport block size (TBS) in a downlink data channel. The methodmay include: receiving channel state information from a terminal;determining an MCS index and a number of PRBs based on i) an MCS tablehaving at least one of TBS indices set to be identical to MCS indices,ii) a TBS table including TBS indices, and iii) the channel stateinformation; and transmitting, to the terminal, downlink controlinformation including the determined MCS index and the number of PRBs.

In accordance with another aspect of the present disclosure, there isprovided a terminal that receives data The terminal may include atransmitting unit, a receiving unit, and a controller. The transmittingunit is configured to transmit channel state information to a basestation. The receiving unit is configured to receive downlink controlinformation from the base station. The controller is configured to:determine a modulation order used in a downlink data channel based on i)an MCS table having at least one of TBS indices set to be identical toMCS indices, and ii) an MCS index included in the downlink controlinformation; and determine a transport block size (TBS) in the downlinkdata channel based on a TBS table including TBS indices, and a TBS indexindicated by the MCS index included in the downlink control information.

In accordance with another aspect of the present disclosure, there isprovided a base station that transmits data The base station may includea receiving unit, a transmitting unit, and a controller. The receivingunit is configured to receive channel state information from a terminal.The transmitting unit is configured to transmit downlink controlinformation to the terminal. The controller is configured to determinean MCS index and a number of PRBs based on i) an MCS table having atleast one of TBS indices set to be identical to MCS indices, ii) a TBStable including TBS indices, and iii) channel state information; andgenerate downlink control information including the determined MCS indexand the number of PRBs.

According to the present disclosure, there is provided a method andapparatus for determining a modulation method and a TBS in a downlinkdata channel for a terminal that uses an LTE network and a low datatransmission rate, and for configuring downlink control information.

Also, according to the present disclosure, a configuration scheme ofdownlink control information is changed based on the channel property ofa terminal that uses an LTE network, and thus, an unnecessary signalingoverhead may be reduced when the downlink control information istransmitted to the terminal that uses a low data transmission rate.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features, and advantages of the presentdisclosure will be more apparent from the following detailed descriptiontaken in conjunction with the accompanying drawings, in which:

FIG. 1 is a table including Maximum Coupling Loss (MCL) values thatrepresent a link budget of each physical channel in an LTE MTC terminal;

FIG. 2 is a table that indicates a degree of coverage improvement foreach physical channel, which is required to satisfy a target MCL valuelisted in the table of FIG. 1;

FIG. 3 is a table illustrating a relationship among a modulation andcoding scheme (MCS) index, a modulation order, and a transport blocksize (TBS) index;

FIG. 4 is a typical CQI index table;

FIG. 5 is a graph illustrating CQI Block Error Rate (BLER) performance;

FIG. 6 is a mapping table between a typical CQI index table and an MCSindex and a TBS index.

FIG. 7 is a table illustrating a TBS value based on a TBS index and thenumber of PRBs;

FIG. 8 is a diagram illustrating a coding method of a data channel;

FIG. 9 is a table illustrating a code block size that allowsturbo-coding;

FIG. 10 is diagram table illustrating the number of TBS entries that areavailable when a method of determining a TBS by an MTC terminal based onscheduling information of conventional downlink control information isused;

FIG. 11 is a table illustrating an average padding overhead for eachvalue corresponding to the number of PRBs when a method of determining aTBS by an MTC terminal based on scheduling information of conventionaldownlink control information is used;

FIGS. 12 and 13 are diagrams for describing a scheme that configuresdownlink control information in a normal coverage according to a firstembodiment of the present disclosure;

FIGS. 14 and 15 are diagrams for describing a scheme that configuresdownlink control information in a normal coverage according to a secondembodiment of the present disclosure;

FIGS. 16 and 17 are diagrams for describing a scheme that configuresdownlink control information in a normal coverage according to a thirdembodiment of the present disclosure;

FIGS. 18 to 21 are diagrams for describing a scheme that configuresdownlink control information in an extended coverage according to afourth embodiment of the present disclosure;

FIGS. 22 to 27 are diagrams for describing a scheme that configuresdownlink control information in an extended coverage according to afifth embodiment of the present disclosure;

FIG. 28 is a diagram illustrating operations of a terminal according tothe present disclosure;

FIG. 29 is a diagram illustrating operations of a base station accordingto an embodiment of the present disclosure;

FIG. 30 is a diagram illustrating a configuration of a terminalaccording to the present disclosure; and

FIG. 31 is a diagram illustrating a configuration of a base stationaccording to the present disclosure.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Hereinafter, some embodiments of the present disclosure will bedescribed in detail with reference to the accompanying illustrativedrawings. In designating elements of the drawings by reference numerals,the same elements will be designated by the same reference numeralsalthough they are shown in different drawings. Further, in the followingdescription of the present disclosure, a detailed description of knownfunctions and configurations incorporated herein will be omitted when itmay make the subject matter of the present disclosure rather unclear.

In addition, terms, such as first, second, A, B, (a), (b) or the likemay be used herein when describing components of the present disclosure.These terms are merely used to distinguish one component from othercomponents, and the property, order, sequence and the like of thecorresponding component are not limited by the corresponding term. Inthe case that it is described that a certain structural element “isconnected to”, “is coupled to”, or “is in contact with” anotherstructural element, it should be interpreted that another structuralelement may “be connected to”, “be coupled to”, or “be in contact with”the structural elements as well as that the certain structural elementis directly connected to or is in direct contact with another structuralelement.

In the present specifications, a machine type communication (MTC)terminal refers to a low cost or low complexity terminal, a terminalthat supports coverage enhancement, or the like. Alternatively, in thepresent specifications, the MTC terminal refers to a terminal that isdefined as a predetermined category for maintaining low costs (or lowcomplexity) and/or coverage enhancement.

In other words, in the present specifications, the MTC terminal mayrefer to a newly defined 3GPP Release 13 low cost (or low complexity) UEcategory/type, which executes LTE-based MTC related operations.Alternatively, in the present specifications, the MTC terminal may referto a UE category/type that is defined in or before 3GPP Release-12 thatsupports the enhanced coverage in comparison with the existing LTEcoverage, or supports low power consumption, or may refer to a newlydefined Release 13 low cost(or low complexity) UE category/type.

The wireless communication system may be widely installed so as toprovide various communication services, such as a voice service, packetdata, and the like.

The wireless communication system may include a User Equipment (UE) anda Base Station (BS or an eNB). Throughout the specifications, the userequipment may be an inclusive concept indicating a user terminalutilized in wireless communication, including a UE (User Equipment) inwideband code division multiple access (WCDMA), long term evolution(LTE), high speed packet access (HSPA), and the like, and an MS (Mobilestation), a UT (User Terminal), an SS (Subscriber Station), a wirelessdevice, and the like in global system for mobile communication (GSM).

A base station or a cell may generally refer to a station wherecommunication with a User Equipment (UE) is performed. The base stationor cell may also be referred to as a Node-B, an evolved Node-B (eNB), aSector, a Site, a Base Transceiver System (BTS), an Access Point, aRelay Node, a Remote Radio Head (RRH), a Radio Unit (RU), and the like.

That is, a base station or cell may be construed as an inclusive conceptindicating a portion of an area covered by a BSC (Base StationController) in CDMA, a NodeB in WCDMA, an eNB or a sector (site) in LTE,and the like, and the concept may include various coverage areas, suchas a megacell, a macrocell, a microcell, a picocell, a femtocell, acommunication range of a relay node, and the like.

Each of the above mentioned various cells has a base station thatcontrols a corresponding cell, and thus, the base station may beconstrued in two ways.

i) the base station may be a device itself that provides a megacell, amacrocell, a microcell, a picocell, a femtocell, and a small cell inassociation with a wireless area, or ii) the base station may indicate awireless area itself.

In i), a base station may be all devices controlled by one entity orcooperating with each other for configuring a predetermined wirelessarea. Based on a configuration type of a wireless area, an eNB, anremote radio head (RRH), an antenna, an radio unit (RU), a Low PowerNode (LPN), a point, a transmission/reception point, a transmissionpoint, a reception point, and the like may be embodiments of a basestation.

In ii), a base station may be a wireless area itself that receives ortransmits a signal from a perspective of a terminal or a neighboringbase station.

Therefore, a megacell, a macrocell, a microcell, a picocell, afemtocell, a small cell, an RRH, an antenna, an RU, an LPN, a point, aneNB, a transmission/reception point, a transmission point, and areception point are commonly referred to as a base station.

In the specification, the user equipment and the base station are usedas two (uplink or downlink) inclusive transceiving subjects to embodythe technology and technical concepts described in the specifications,and may not be limited to a predetermined term or word.

Here, Uplink (UL) refers to a scheme for a UE to transmit and receivedata to/from a base station, and Downlink (DL) refers to a scheme for abase station to transmit and receive data to/from a UE.

Varied multiple access schemes may be unrestrictedly applied to thewireless communication system. Various multiple access schemes mayinclude CDMA (Code Division Multiple Access), TDMA (Time DivisionMultiple Access), FDMA (Frequency Division Multiple Access), OFDMA(Orthogonal Frequency Division Multiple Access), OFDM-FDMA, OFDM-TDMA,OFDM-CDMA.

An embodiment of the present disclosure may be applicable to resourceallocation in an asynchronous wireless communication scheme that isadvanced through GSM, WCDMA, and HSPA, to be LTE and LTE-advanced.Embodiments of the present disclosure may be also applicable to resourceallocation in a synchronous wireless communication scheme that isadvanced through CDMA and CDMA-2000, to be UMB. Embodiments of thepresent disclosure may not be limited to a specific wirelesscommunication field. Embodiments of the present disclosure may beapplicable to other related technical fields.

Uplink transmission and downlink transmission may be performed based ona TDD (Time Division Duplex) scheme or an FDD (Frequency DivisionDuplex). The TDD scheme performs transmission based on different times.The FDD scheme performs transmission based on different frequencies.

Further, in a system such as LTE and LTE-A, a related standard maydefine that an uplink and a downlink are configured based on a singlecarrier or a pair of carriers. The uplink and the downlink may transmitcontrol information through a control channel, such as a PDCCH (PhysicalDownlink Control CHannel), a PCFICH (Physical Control Format IndicatorCHannel), a PITCH (Physical Hybrid ARQ Indicator CHannel), a PUCCH(Physical Uplink Control CHannel), an EPDCCH(Enhanced Physical DownlinkControl CHannel), and the like. The uplink and the downlink may transmitdata through a data channel, such as a PDSCH (Physical Downlink SharedCHannel), a PUSCH (Physical Uplink Shared CHannel), and the like.

Control information may be transmitted using an EPDCCH (enhanced PDCCHor extended PDCCH).

In the present specification, a cell may refer to the coverage of asignal transmitted from a transmission/reception point, a componentcarrier having the coverage of the signal transmitted from thetransmission/reception point (transmission point ortransmission/reception point), or the transmission/reception pointitself.

A wireless communication system according to embodiments refers to aCoordinated Multi-point transmission/reception (CoMP) system, acoordinated multi-antenna transmission system, or a coordinatedmulti-cell communication system, where two or moretransmission/reception points cooperatively transmit a signal. A CoMPsystem may include at least two multi-transmission/reception points andterminals.

A multi-transmission/reception point may be a base station, a macro cell(hereinafter, referred to as an ‘eNB’), or at least one RRH. The RRH isconnected to the eNB through an optical cable or an optical fiber, iswiredly controlled, and has a high transmission power or a lowtransmission power within a macro cell area.

Hereinafter, a downlink refers to communication or a communication pathfrom a multi-transmission/reception point to a terminal, and an uplinkrefers to communication or a communication path from a terminal to amulti-transmission/reception point. In a downlink, a transmitter may bea part of a multiple transmission/reception point and a receiver may bea part of a terminal. In an uplink, a transmitter may be a part of aterminal and a receiver may be a part of a multipletransmission/reception point.

Hereinafter, the situation in which a signal is transmitted and receivedthrough a PUCCH, a PUSCH, a PDCCH, an EPDCCH, a PDSCH, or the like maybe described through the expression, “a PUCCH, a PUSCH, a PDCCH, anEPDCCH, or a PDSCH is transmitted or received”.

In addition, hereinafter, the expression “a PDCCH is transmitted orreceived, or a signal is transmitted or received through a PDCCH”includes “an EPDCCH is transmitted or received, or a signal istransmitted or received through an EPDCCH”.

That is, a physical downlink control channel used herein may indicate aPDCCH or an EPDCCH. Alternatively, the physical downlink control channelmay indicate both a PDCCH and an EPDCCH.

In addition, for ease of description, an EPDCCH, which corresponds to anembodiment of the present disclosure, may be applied to the partdescribed using a PDCCH and to the part described using an EPDCCH.

Meanwhile, higher layer signaling includes an RRC signaling thattransmits RRC information including an RRC parameter.

An eNB performs downlink transmission to terminals. The eNB may transmita Physical Downlink Shared Channel (PDSCH) which is a primary physicalchannel for unicast transmission. The eNB may transmit a PhysicalDownlink Control Channel (PDCCH) for transmitting downlink controlinformation, such as scheduling required for reception of a PDSCH, andscheduling grant information for transmission of an uplink data channel(for example, a Physical Uplink Shared Channel (PUSCH)). Hereinafter,transmission and reception of a signal through each channel will bedescribed as transmission and reception of a corresponding channel.

A machine type communication (MTC) is defined as communication betweendevices or objects without human intervention. From the perspective of3GPP, “machine” indicates an entity that does not require a user'sdirect operation or intervention, and “MTC” is defined as a type of datacommunication including one or more machines.

A representative example of the machine may include a smart meter,vending machine, or the like, which is equipped with a mobilecommunication module. However, as a smart phone has been introduced thatautomatically accesses a network and executes communication withoutuser's operation or intervention based on the location or situation of auser, a portable terminal having an MTC function has been considered asa type of machine.

[LTE-Based Low-Cost MTC]

As an LTE network has been widely used, mobile carriers desire tominimize the number of radio access terminals (RATs) in order to reducemaintenance costs of the network or the like. However, the number oftypical GSM/GPRS network-based MTC products has been increasing, and anMTC that uses a low data transmission rate can be provided at a lowcost. Therefore, the LTE network is used for a general datatransmission, and the GSM/GPRS network is used for MTC, and thus, themobile carriers need to separately operate two RATs, and this may causeinefficiency in utilizing a frequency band, which carries a financialburden to the mobile carriers.

To solve the above drawback, a cheap MTC terminal that uses theGSM/EGPRS network needs to be replaced with an MTC terminal that uses anLTE network. To this end, various requirements to decrease the price ofthe LTE MTC terminal have been discussed in the 3GPP RAN WG1 standardsconference. Also, the standards conference writes a technical document(TR 36.888) including various functions that may be provided to satisfythe requirements.

A main item that is associated with changing a physical layer standardand is currently discussed in 3GPP to support the low-cost LTE MTCterminal may be a technology for supporting a narrow band/single RFchain/half duplex FDD/long discontinued reception (DRX), or the like.However, the methods that are considered to decrease the price maydecrease the performance of an MTC terminal when compared to a legacyLTE terminal.

Also, about 20% of the MTC terminals that support an MTC service, suchas smart metering, are installed in a deep indoor environment (e.g., abasement). To perform successful MTC data transmission, the coverage ofan LTE MTC terminal needs to be improved by about 15 [dB] when comparedto the coverage of a legacy normal LTE terminal.

FIG. 1 is a table including maximum coupling loss (MCL) values eachrepresenting a link budget of each physical channel in an LTE MTCterminal. An FDD PUSCH has the smallest MCL value, and thus, a targetMCL value for an improvement of about 15 [dB] is 140.7+15=155.7 [dB].

FIG. 2 is a table including a degree of coverage improvement for eachphysical channel, which is required to satisfy a target MCL value listedin the table of FIG. 1.

To lower the price of an LTE MTC terminal and to increase the coverage,various methods for a robust transmission, such as PSD boosting, lowcoding rate, and time domain repetition, or the like, are considered foreach physical channel.

The requirements of an LTE-based low-cost MTC terminal are as follows:

-   -   A data transmission speed should satisfy at least a data        transmission speed provided by an EGPRS-based MTC terminal, that        is, downlink 118.4 kbps, uplink 59.2 kbps.    -   Frequency efficiency should be dramatically improved when        compared to a GSM/EGPRS MTC terminal.    -   A provided service area should not be smaller than that of a        GSM/EGPRS MTC terminal.    -   An amount of power consumption should not be larger than a        GSM/EGPRS MTC terminal.    -   A legacy LTE terminal and an LTE MTC terminal can be used in the        same frequency.    -   An existing LTE/SAE network is reused.    -   Optimization is performed in a TDD mode, in addition to an FDD        mode.    -   A low-cost LTE MTC terminal should support a limited mobility        and a low-power consumed module.

A modulation method used for downlink data transmission in 3GPP LTEincludes QPSK, 16QAM, and 64QAM. A base station selects one of the threemodulation methods based on a downlink channel state, and reports thesame to the terminal using Downlink Control Information (DCI).

FIG. 3 is a table showing a relationship between an MCS index formed of5 bits, a modulation order, and a TBS index.

Referring to FIG. 3, the MCS index formed of 5 bits in downlink controlinformation (DCI) may inform a terminal of three types of modulationmethods. In FIG. 3, MCS indices from 0 to 28 are used for hybridautomatic repeat request (HARQ) initial transmission, and MCS indices 29to 31 are used for HARQ retransmission.

More specifically, MCS indices #0 to #9 imply that a QPSK modulationmethod is used for DL data transmission, MCS indices #10 to #16 implythat a 16QAM modulation method is used therefor, and MCS indices #17 to#28 imply that a 64QAM modulation method is used therefor.

As described above, a plurality of MCS indices exists for an identicalmodulation scheme, and each MSC index indicates that data may betransmitted using code words having different coding rates. When achannel state is good, a base station uses a high MCS index to increasebandwidth efficiency, and when the channel state is poor, the basestation uses a low MCS index and executes robust transmission so as toovercome the channel state. A method of adjusting an MCS to beappropriate for the channel state is referred to as link adaptation.

When the MCS indices from 0 to 28 are used for HARQ initialtransmission, the MCS indices 29, 30, and 31 are used for distinguishinga modulation scheme used for HARQ retransmission. Therefore, the MCSindex 29 indicates that the QPSK modulation is used for HARQretransmission, the MCS index 30 indicates that the 16QAM modulation isused for HARQ retransmission, and the MCS index 31 indicates that the64QAM modulation is used for HARQ retransmission.

A terminal needs to feed a channel state back to a base station so thatthe base station performs link adaptation based on the channel state ofthe terminal. Channel state information that the terminal feeds back tothe base station is referred to as channel state information (CSI), andthe CSI includes a pre-coding matrix indicator (PMI), a rank indicator(RI), and a channel quality indicator (CQI).

Here, the PMI and the RI is channel state information associated with aMIMO transmission. The CQI indicates a modulation method, a code rate,and a transmission efficiency (Efficiency=modulation order*code rate)that may be used based on the channel state of a terminal, asillustrated in FIG. 4. The terminal feeds back a CQI index of hightransmission efficiency when the channel state is good. The terminalfeeds back a CQI index of low transmission efficiency when the channelstate is poor. The size of typical CQI feedback information is 4 bitsand indicates a total of 16 types of transmission efficiencies.

FIG. 5 is a graph showing a CQI BLER performance. The graph of FIG. 5includes SNR values that satisfy BLER 10% as compared to transmissionefficiency and illustrates performance of a CQI of FIG. 4 in anexperimental environment that simulates an AWGN channel environmenthaving a single transmission antenna and two reception antennas.

Referring to FIG. 5, in the case of the typical CQI, the required SNR ofBLER 10% ranges from about −10 dB to 17 dB. Each CQI index has atransmission efficiency that is set to have regular SNR intervals ofabout 1.9 dB.

A base station determines a CQI received from a terminal and determinesan amount of resources to be allocated to the terminal and an MCS to beused for transmission, based on the received CQI. In this instance, theMCS of FIG. 3 and the CQI of FIG. 4 have a relationship of FIG. 6.

MCS indices 0, 2, 4, 6, 8, 11, 13, 15, 18, 20, 22, 24, 26, and 28 areset to have transmission efficiencies that are identical to thetransmission efficiencies of the CQI indices 2, 3, 4, 5, 6, 7, 8, 9, 10,11, 12, 13, 14, and 15, respectively. In addition, between twoconsecutive CQI indices, an MCS index is set that has a transmissionefficiency corresponding to an intermediate between transmissionefficiencies supported by the two CQI indices.

The MCS indices 9 and 10, of which a modulation order is changed from 2to 4 (from QPSK to 16QAM), are set to have the same transmissionefficiency. Also, the MCS indices 16 and 17, of which a modulation orderis changed from 4 to 6 (from 16QAM to 64QAM), are set to have the sametransmission efficiency. In addition, MCS indices having differentmodulation orders are set to have an identical TBS index, and thus, thesame amount of TBS is transmitted through the same amount oftransmission resource.

In FIG. 3, a TBS index I_(TBS) is set for each MCS index I_(MCS). In3GPP TS 36.213, by taking into consideration that the number of PRBpairs (N_(PRB)) that ranges from 1 to 110, which corresponds to the sizeof a transmission resource, is allocated to a terminal, 110 TBSscorresponding to transmittable information bit sizes are defined foreach I_(TBS).

FIG. 7 is a table illustrating TBS values used when an N_(PRB) value is1 to 6.

The base station determines a channel state through a CQI received froma terminal and selects the size of a transmission resource to beallocated to the terminal and an MCS to be used for the correspondingtransmission resource, based on the determined channel state. In thisinstance, determining a code rate of an MCS is equal to determining aTBS, which is a size of information bits to be transmitted through thecorresponding transmission resource.

Therefore, to inform the terminal of a TBS, the base station uses thenumber of PRB pairs and an MCS index formed of 5 bits, which areincluded in scheduling information of downlink control information(DCI).

For example, when the scheduling information included in the DCIindicates that the number of PRB pairs N_(PRB)=4 and the MCS indexI_(MCS)=7, it indicates that a TBS entry corresponding to the TBS indexI_(TBS)=7 is TBS=472.

FIG. 8 illustrates a method of encoding an LTE data channel. Referringto FIG. 8, a method of encoding a channel based on a set TBS will bedescribed.

Referring to FIG. 8, when a TBS is set, a base station cuts a single MACPDU based on a TBS or generates a transport block (TB) by aggregating aplurality of MAC PDUs based on a TBS.

Before inputting the same into a channel encoder, the method generates aTB CRC formed of 24 bits using a TB, as illustrated in FIG. 8. Themethod attaches the generated TB CRC to the end of a TB bit stream. Whenthe sum of the size of the TB and the TB CRC formed of 24 bits isgreater than 6144 bits, code block segmentation is executed. In thisinstance, a code block (CB) CRC formed of 24 bits is added to each codeblock, and the size of a code block including the CB CRC is not greaterthan 6144 bits. Each code block is encoded into a turbo code.

When the code block segmentation is executed on a TB, B, whichdetermines the number C of code blocks, is a value including a TBS and aTB CRC. Therefore, B=A+24. In FIG. 8, an information bit streamincluding the TB CRC is expressed by b₀, b₁, . . . , and b_(B−1).

When B is less than or equal to 6144 bits, which is the largest size ofa code block, the number C of code blocks is 1, and the code blocksegmentation of a TB is not executed. In addition, the number C of codeblocks is 1, and thus, an additional CB CRC is not required. Therefore,the total number B′ of information bits that are turbo-encoded is equalto B. When B is greater than 6144 bits, the code block segmentation of aTB is executed, and the number C of code blocks is C=┌B/(Z−L)┐. Inaddition, a CB CRC formed of 24 bits is included in each code block.Therefore, the total number B′ of information bits that are encoded isB′=B+24*C.

The code block segmentation method defines the number C of code blocksbased on B′ and determines a code block size K, which allowsturbo-encoding.

FIG. 9 is a table that illustrates a code block size K that allowsturbo-encoding. K uses 188 block sizes that are defined in advance inthe range of 40 to 6144 bits (3GPP TS 36.212, Table 5.1.3-3: K isdefined in Turbo code internal interleaver parameters).

A base station is capable of performing resource allocation of a maximumof 6 PRB pairs in a single subframe with respect to an MTC terminal, andthe maximum available TBS is 1000 bits. Also, only QPSK and 16 QAM areused as a data modulation method, and 64 QAM is not used.

Therefore, when the base station informs an MTC terminal of a TBS basedon a typical method, the typical TBS table may include TBS entries thatare not used. Particularly, a TBS entry having an I_(TBS) that isgreater than or equal to 16 corresponds to the

TBS entry that uses 64QAM and thus, the TBS entry is not used. Also,when N_(PRB) is 4, 5, and 6, and I_(TBS) is 14, 12, and 10 or higher,respectively, a TBS is greater than 1000 bits and thus, a correspondingTBS entry is not used.

FIG. 10 is a table that illustrates the number of available TBS entrieswhen an MTC terminal determines a TBS based on the typical schedulinginformation, which illustrates the number of available TBS entries whenN_(PRB) ranges from 1 to 6.

Therefore, in the typical DCI scheduling information, the number of TBSentries that the MTC terminal may determine is relatively smaller than5-bit MCS signaling, and thus, unnecessary signaling overhead may exist.Also, only the limited number of TBSs among TBS values ranges from atleast 16 bits to a maximum of 1000 bits are defined for each N_(PRB),and thus, a TBS value that can be selected during scheduling may belimited.

For example, in consideration of an MTC application that transmits arelatively small data packet size is considered, a difference between aTBS and an adjacent sized TBS is set to be large, and thus, a paddingoverhead increases when a MAC PDU is generated.

FIG. 11 is a table that illustrates a result of calculating averagepadding overhead for each N_(PRB) when a value obtained by dividing thedifference between two TBSs corresponding to consecutive I_(TBS) withrespect to TBSs defined for each N_(PRB) by a large TBS value out of thetwo TBSs, is defined as a padding overhead.

Also, in a case of an MTC terminal of which the coverage is extended, anMCS index included in the typical scheduling information is transmittedwith significantly low spectral efficiency using repetitivetransmission, irrespective of a spectral efficiency used for the actualtransmission. However, when a TBS value is determined based on N_(PRB),the number of PRB pairs allocated for each subframe needs to be limitedto determine a predetermined TBS value.

For example, to use TBS=16, the number of PRB pairs that is allocatedfor each subframe needs to always be one. Therefore, repetitivetransmission is performed using only 1 PRB pair for each subframe.Alternatively, when the number of PRB pairs transmitted for eachsubframe is fixed or a separate signaling is used, an additionalsignaling overhead for N_(PRB) is required to determine a TBS value.

Scheduling information for a TBS value is included in DCI as MCS and PRBallocation information, and the scheduling information may betransmitted to a terminal. In this instance, the used DCI is definedaccording to the number of repetitive transmissions based on thecoverage level of an MTC terminal, as follows:

-   -   DCI format used for scheduling PDSCH for no and small repetition        levels. (=DCI format M1A)    -   DCI format used for scheduling PDSCH for other repetition        levels. (=DCI format M1B)    -   DCI format used for scheduling PUSCH for no and small repetition        levels. (=DCI format M0A)    -   DCI format used for scheduling PUSCH for other repetition        levels. (=DCI format M0B)

According to an example, a case in which the number of repetitivetransmissions is less than or equal to 2 is referred to as no and smallrepetition levels, and a case in which the number of repetitivetransmissions is greater than 2 is referred to as other repetitionlevels. However, the present disclosure may not be limited thereto.

Using a DCI format that is different based on the coverage level of anMTC terminal, a base station transmits the scheduling information to theterminal.

When the coverage of the MTC terminal corresponds to the coverage levelof a legacy normal LTE terminal, the repetitive transmission of aphysical channel may not be needed or a fewer number of repetitivetransmissions may be needed to perform the physical channel transmissionbetween the base station and the terminal. The base station transmitsscheduling information of the physical channel to an MTC terminal usinga DCI format M1A/M0A. In this instance, the used MCS information informsthe terminal of a modulation method, such as QPSK or 16QAM.

When an MTC terminal is located in the coverage that is extended to belarger than the coverage level of a normal terminal, the base stationtransmits scheduling information of a physical channel to the MTCterminal using DCI format M1B/M0B. In this instance, the MCS informationinforms the terminal of only QPSK modulation method.

The present disclosure proposes to define and use MCS tables to be usedfor DCI format M1A/M0A or DCI format M1B/M0B, respectively.

Also, the present disclosure proposes a method of determining a TBSusing scheduling information and the typical TBS table, in the case ofDCI format M1A/M0A. In the case of DCI format M1B/M0B, the presentdisclosure proposes a method that defines a new TBS table to be used foran MTC terminal, and determines a TBS using the scheduling informationof DCI format M1B/M0B.

[Method of Configuring MCS for DCI Format M1A/M0A]

First Embodiment

FIG. 12 and FIG. 13 illustrate a scheme of configuring downlink controlinformation (DCI) that is transmitted to an MTC terminal of a normalcoverage according to a first embodiment of the present disclosure. FIG.12 is a table illustrating a relationship among an MCS index, amodulation order, and a TBS index. FIG. 13 is a table illustrating a TBSbased on a TBS index and the number of PRB pairs.

FIG. 12 is an MCS table for an MTC terminal when 4 bits are used as thenumber of signaling bits required for an MCS information transmission ofDCI format M1A/M0A.

When compared to the typical MCS table, the MCS table includesI_(TBS)=15, which is the largest index among 16QAM MCS entries, and theMCS table is designed to use only QPSK with respect to I_(TBS)=9, whichis a TBS index after which QPSK is changed to 16QAM. Therefore, QPSK isused when the MCS index I_(MCS) ranges from 0 to 9, and 16QAM is usedwhen the MCS index I_(MCS) ranges from 10 to 15. Also, I_(TBS) andI_(MCS) are designed to have the same value.

FIG. 13 illustrates a TBS value that an MTC terminal uses in the typicalTBS table when the MCS table of FIG. 12 is used.

Second Embodiment

FIG. 14 and FIG. 15 illustrate a scheme of configuring downlink controlinformation (DCI) that is transmitted to an MTC terminal in a normalcoverage according to a second embodiment of the present disclosure.FIG. 14 is a table illustrating a relationship among an MCS index, amodulation order, and a TBS index. FIG. 15 is a table illustrating a TBSbased on a TBS index and the number of PRB pairs.

FIG. 14 is an MCS table for an MTC terminal when 3 bits are used as thenumber of signaling bits required for an MCS information transmission ofDCI format M1A/M0A.

Referring to FIG. 14, QPSK is used when the MCS index I_(MCS) rangesfrom 0 to 4, and 16QAM is used when the MCS index I_(MCS) ranges from 5to 7. Also, it is designed to use a value of I_(TBS)=I_(MCS)*2.

FIG. 15 illustrates a TBS value that an MTC terminal uses in the typicalTBS table when the MCS table of FIG. 14 is used.

Third Embodiment

FIG. 16 and FIG. 17 are tables for describing a scheme of configuringdownlink control information (DCI) that is transmitted to an MTCterminal in a normal coverage according to a third embodiment of thepresent disclosure. FIG. 16 is a table illustrating a relationship amongan MCS index, a modulation order, and a TBS index. FIG. 17 is a tableillustrating a TBS based on a TBS index and the number of PRB pairs.

FIG. 16 is an MCS table for an MTC terminal when 3 bits are used as thenumber of signaling bits required for an MCS information transmission ofDCI format M1A/M0A. Therefore, QPSK is used when the MCS index I_(MCS)ranges from 0 to 4, and 16QAM is used when the MCS index I_(MCS) rangesfrom 5 to 7. Also, unlike the second embodiment, the MCS table in thethird embodiment is designed to use a value of I_(TBS)=I_(MCS)*2+1.

FIG. 17 illustrates a TBS value that an MTC terminal uses in the typicalTBS table when the MCS table of FIG. 16 is used.

According to the above described first embodiment, second embodiment,and third embodiment, i) information associated with the number of PRBsused for each subframe irrespective of the number of repetitivelytransmitted subframes and ii) an MCS index value proposed by the presentdisclosure may be used to determine a TBS value using schedulinginformation included in DCI format M1A/M0A.

Also, in the case in which a TBS value is determined using thescheduling information included in DCI format M1A/M0A, the TBS value maybe changed to 1000 bits, and the changed TBS value may be used if theTBS value is greater than or equal to 1000 bits, which is the maximumTBS that may be transmitted to an MTC terminal.

Alternatively, in the case in which a TBS value is determined using thescheduling information included in DCI format M1A/M0A, the TBS value maybe changed to be less than or equal to 1000 bits, and the changed TBSvalue may be used if the TBS value is greater than or equal to 1000bits, which is the maximum TBS that may be transmitted to an MTCterminal. In this instance, the modulation method used may be changed toQPSK.

[Method of Configuring MCS for DCI Format M1B/M0B]

Fourth Embodiment

FIG. 18 to FIG. 21 are diagrams for describing a scheme of configuringdownlink control information (DCI) that is transmitted to an MTCterminal in an extended coverage according to a fourth embodiment of thepresent invention.

FIG. 18 is an MCS table for an MTC terminal when 4 bits are used as thenumber of signaling bits required for an MCS information transmission ofDCI format M1B/M0B. It is designed to use QPSK with respect to all MCSindices. Also, it is designed that I_(TBS) and I_(MCS) have the samevalue.

I_(TBS) in FIG. 18 indicates a TBS index in a TBS table that is newlydesigned for an MTC terminal, as opposed to the typical TBS table.

According to the fourth embodiment, to determine a TBS value usingscheduling information used for DCI format M1B/M0B, only a TBS indexbased on an MCS index value proposed in the present disclosure is used,irrespective of information associated with the number of repetitivelytransmitted subframes and the number of PRBs used for each subframe.

FIG. 19 illustrates an example of a new TBS table for an MTC terminalfor the fourth embodiments that uses 4 bits as the number of MCSsignaling bits. In FIG. 19, a TBS table is designed to increase apadding overhead to be proportional to a TBS value by taking intoconsideration of a difference between the sizes of adjacent TBSs within1000 bits as a padding overhead.

FIG. 20 illustrates a TBS table that is designed using a high frequentTBS value out of TBSs of FIG. 13 determined based on DCI format M1A/M0A,as another example of a new TBS table for an MTC terminal used inassociation with the fourth embodiment that uses 4 bits as the number ofMCS signaling bits.

FIG. 21 illustrates a TBS of which a TBS value is used at least twotimes, and the number of times that the TBS value is used.

Fifth Embodiment

FIG. 22 to FIG. 27 are diagrams for describing a scheme of configuringdownlink control information (DCI) that is transmitted to an MTCterminal in an extended coverage according to a fifth embodiment of thepresent disclosure.

FIG. 22 illustrates an MCS table for an MTC terminal when 3 bits areused as the number of signaling bits required for an MCS informationtransmission of DCI format M1B/M0B. It is designed that QPSK is usedwith respect to all MCS indices, and also, I_(TBS) and I_(MCS) are tohave the same value.

I_(TBS) in FIG. 22 indicates a TBS index in a TBS table that is newlydesigned for an MTC terminal, as opposed to the typical TBS table.

According to the fifth embodiment, to determine a TBS value usingscheduling information used for DCI format M1B/M0B, only a TBS indexbased on an MCS index value proposed in the present disclosure is used,irrespective of information associated with the number of repetitivelytransmitted subframes and the number of PRBs used for each subframe.

FIG. 23 illustrates an example of a new TBS table for an MTC terminalused in the fifth embodiment that uses 3 bits as the number of MCSsignaling bits.

A TBS table illustrated in FIG. 23 is designed to increase a paddingoverhead to be proportional to a TBS value by taking into considerationof a difference between the sizes of adjacent TBSs within 1000 bits as apadding overhead.

FIG. 24 illustrates a TBS table that is designed using a high frequentTBS value out of TBSs of FIG. 15 determined based on DCI format M1A/M0A,as another example of a new TBS table for an MTC terminal in associationwith the fifth embodiment that uses 3 bits as the number of MCSsignaling bits.

FIG. 25 illustrates a TBS of which a TBS value of FIG. 15 is used atleast two times, and the number of times that the TBS value is used.

FIG. 26 illustrates a TBS table that is designed using a high frequentTBS value out of TBSs of FIG. 17 determined based on DCI format M1A/M0A,as another example of a new TBS table for an MTC terminal in associationwith the fifth embodiment that uses 3 bits as the number of MCSsignaling bits.

FIG. 27 illustrates a TBS of which a TBS value of FIG. 17 is used atleast two times, and the number of times that the TBS value is used.

Sixth Embodiment

As another method of configuring an MCS table for DCI format M1B/M0B,DCI format M1B/M0b may equally use the MCS table of DCI format M1A/M0Aproposed in the present disclosure based on the number of MCS signalingbits. In this instance, QPSK may be fixedly used as a modulation method,irrespective of an MCS index.

When information associated with the number of PRBs exists in schedulinginformation included in DCI format M1B/M0B, a TBS value may bedetermined in the same manner as the method of determining a TBS byusing DCI format M1A/M0A, which is proposed in the present disclosure.

When the information associated with the number of PRBs does not existin the scheduling information included in DCI format M1B/M0B, 6 PRBscorresponding to a single narrow band may be used for each subframe. Inthis instance, the TBS value may be determined by fixing a N_(PRB) valueto a predetermined value and by using a TBS index indicated by thetypical TBS table and the MCS table.

Here, the N_(PRB) value may be a predetermined value or signaling. Forexample, the N_(PRB) value may be fixed to 3 or 4.

FIG. 28 is a flowchart illustrating a method for an MTC terminal toreceive downlink control information (DCI) from a base station and todetermine a modulation method and a TBS used in a downlink data channelaccording to an embodiment of the present disclosure.

Referring to FIG. 28, a MTC terminal according to an embodiment of thepresent disclosure measures a channel state and transmits channel stateinformation (CSI) including the measured channel state to a base stationin operation S2800.

The MTC terminal receives, from the base station, downlink controlinformation (DCI) including a 4-bit MCS index determined based on theCSI in operation S2810.

The MTC terminal determines the MCS index included in the CSI inoperation S2820. The MTC terminal determines a modulation orderindicated by the MCS index that is determined in an MCS table in whichsome or all of TBS indices are set to be the same as MCS indices inoperation S2830.

In this instance, when the MTC terminal is an MTC terminal existing in anormal coverage, a modulation method based on the modulation orderindicated by the determined MCS index may be QPSK or 16QAM. When the MTCterminal is an MTC terminal existing in an extended coverage, amodulation method based on the modulation order indicated by thedetermined MCS index may be an identical method, which is QPSK.

The MTC terminal determines a TBS index indicated by the MCS indexincluded in the DCI in operation S2840. The MTC terminal determines thenumber of PRBs included in the DCI in operation S2850.

The MTC terminal determines a transport block size (TBS) used in adownlink data channel using a TBS index and the number of PRBs, whichare determined from a TBS table including TBS indices and the number ofPRBs, in operation S2860.

FIG. 29 is a flowchart illustrating a method for a base station toconfigure downlink control information (DCI) to be transmitted to an MTC

Referring to FIG. 29, the base station according to an embodiment of thepresent disclosure, receives channel state information (CSI) from theMTC terminal in operation S2900.

The base station determines a transport block size (TBS) and an MCS tobe used in a downlink data channel that is transmitted to the MTCterminal, based on the CSI in operation S2910.

The base station may select an MCS index from an MCS table in which someor all of the TBS indices are set to be the same as MCS indices. In thisinstance, a signaling bit required for an MCS information transmissionis 3 bits or 4 bits.

When the MTC terminal is an MTC terminal existing in a normal coverage,a modulation order indicated by the MCS index in the MCS table may beQPSK or 16QAM.

For example, in a case in which a signaling bit required for an MCSinformation transmission is 4 bits, when an MCS index ranges from 0 to9, QPSK is used as a modulation method. When an MCS index ranges from 10to 15, 16QAM is used as a modulation method.

The base station determines the number of PRBs based on an MCS index anda TBS, which are determined from the TBS table including TBS indices,and generates downlink control information (DCI) including thedetermined MCS index and the number of PRBs in operation S2920.

The base station transmits, to the MTC terminal, the DCI including theMCS index formed of 4 bits and the number of PRBs in operation S2930 sothat the MTC terminal determines a modulation method and a TBS used inthe downlink data channel.

FIG. 30 is a diagram illustrating a configuration of a terminalaccording to an embodiment of the present disclosure.

Referring to FIG. 30, a terminal 3000 according to an embodiment of thepresent disclosure includes a controller 3010, a transmitting unit 3020,and a receiving unit 3030.

The transmitting unit 3020 transmits, to the base station, uplinkcontrol information, data, and a message through a correspondingchannel. Also, the transmitting unit 3020 transmits, to the basestation, channel state information (CSI) including information obtainedby measuring the quality of a channel.

The receiving unit 3030 may receive, from the base station, downlinkcontrol information (DCI), data, a message, through a correspondingchannel. The DCI that is received from the base station may includeinformation associated with an MCS index and the number of PRBs.

The controller 3010 determines a modulation method and a transport blocksize (TBS) used in a downlink data channel, based on the DCI receivedfrom the base station.

The controller 3010 i) determines an MCS index included in the DCI andii) determines a modulation order indicated by an MCS index included inthe DCI from an MCS table in which some or all of the TBS indices areset to be the same as MCS indices. A modulation method used in thedownlink data channel is determined based on the determined modulationorder. When the MTC terminal 3000 is an MTC terminal existing in anormal coverage, the modulation method used in the downlink data channelmay be QPSK or 16QAM. When the MTC terminal 3000 is an MTC terminalexisting in an extended coverage, the modulation method used in thedownlink data channel may be QPSK.

From the MCS table, the controller 3010 determines a TBS index indicatedby the MCS index included in the DCI and determines the number of PRBsincluded in the DCI. The controller 3010 determines a TBS value based ona TBS index and the number of PRBs from a TBS table and determines a TBSused in the downlink data channel.

FIG. 31 illustrates a configuration of a base station according to anembodiment of the present disclosure.

Referring to FIG. 31, a base station 3100 according to an embodiment ofthe present disclosure includes a controller 3110, a transmitting unit3120, and a receiving unit 3130.

The controller 3110 receives channel state information (CSI) from an MTCterminal and determines the size of a resource to be transmitted to theMTC terminal and an MCS based on the received CSI.

The controller 3110 determines an MCS index from an MCS table in whichsome or all of the TBS indices are set to be the same as MCS indices.The controller 3110 determines a TBS from a TBS table including TBSindices and the number of PRBs. The controller 3110 generates downlinkcontrol information (DCI) including the determined MCS index and thenumber of PRBs.

The transmitting unit 3120 and the receiving unit 3130 are used fortransmitting/receiving, to/from the MTC terminal, a signal, a message,or data which is required to implement the present disclosure. Thetransmitting unit 3120 transmits, to the MTC terminal, DCI generated bythe controller 3110 so that the MTC terminal determines, based on theDCI, a modulation order and a transport block size (TBS) that are usedin a downlink data channel.

The content associated with the standard or standard documents,mentioned in the above described embodiments, has been omitted forsimple description of the present specifications, but it may be a partof the present specifications. Therefore, when a part of the content anddocuments associated with the standard is added to the presentspecifications or is specified in claims, it should be construed as apart of the present invention.

Although the exemplary embodiments of the present disclosure have beendescribed for illustrative purposes, those skilled in the art willappreciate that various modifications and substitutions are possible,without departing from the scope and spirit of the present disclosure asdisclosed in the accompanying claims. Therefore, the exemplaryembodiments disclosed in the present disclosure are intended toillustrate the scope of the technical idea of the present disclosure,and the scope of the present disclosure is not limited by the exemplaryembodiments.

1-20. (canceled)
 21. A method of determining, by a terminal, amodulation order and a transport block size (TBS) in a downlink datachannel, the method comprising: receiving, from a base station, downlinkcontrol information; determining the modulation order used in thedownlink data channel using i) a modulation and coding scheme (MCS)table including at least one of TBS indices set to be identical to MCSindices and ii) an MCS index included in the downlink controlinformation; and determining a TBS index using the MCS table and the MCSindex included in the downlink control information, and determining aTBS in the downlink data channel using a TBS table including TBSindices, the determined TBS index and the number of physical resourceblocks (PRBs) included in the downlink control information, wherein,when the number of repetitive transmissions of the downlink data channelis less than or equal to a predetermined number of times, a modulationorder indicated by the MCS index included in the downlink controlinformation is one of QPSK and 16QAM; and wherein, when the number ofrepetitive transmissions of the downlink data channel exceeds apredetermined number of times, a modulation order indicated by the MCSindex included in the downlink control information is identical, each ofall TBS indices mapped from the MCS indices in the MCS table is set tohave a value identical to a corresponding MCS index.
 22. The method ofclaim 21, wherein: in the MCS table, (i) a range of the MCS indices isfrom 0 to 15; (ii) a range of the TBS indices is from 0 to 15; and iii)each of all TBS indices mapped from the MCS indices in the MCS table isset to have a value identical to a corresponding MCS index.
 23. Themethod of claim 21, wherein, when a TBS index indicated by the MCS indexincluded in the downlink control information is identical to the MCSindex, a modulation order indicated by the MCS index included in thedownlink control information is QPSK.
 24. The method of claim 21,wherein a modulation order indicated by the MCS index included in thedownlink control information is QPSK.
 25. A method of determining, by abase station, a modulation order and a transport block size (TBS) in adownlink data channel, the method comprising: receiving channel stateinformation from a terminal; determining an modulation and coding scheme(MCS) index and a number of physical resource blocks (PRBs) based on i)an MCS table having at least one of TBS indices set to be identical toMCS indices, ii) a TBS table including TBS indices, and iii) the channelstate information; and transmitting, to the terminal, downlink controlinformation including the determined MCS index and the number of PRBs,wherein, when the number of repetitive transmissions of the downlinkdata channel is less than or equal to a predetermined number of times, amodulation order indicated by the MCS index included in the downlinkcontrol information is one of QPSK and 16QAM; and wherein, when thenumber of repetitive transmissions of the downlink data channel exceedsa predetermined number of times, a modulation order indicated by the MCSindex included in the downlink control information is identical, each ofall TBS indices mapped from the MCS indices in the MCS table is set tohave a value identical to a corresponding MCS index.
 26. The method ofclaim 25, wherein: in the MCS table, (i) a range of the MCS indices isfrom 0 to 15; (ii) a range of the TBS indices is from 0 to 15; and iii)each of all TBS indices mapped from the MCS indices in the MCS table isset to have a value identical to a corresponding MCS index.
 27. Themethod of claim 25, wherein, when a TBS index indicated by thedetermined MCS index in the MCS table is set to be identical to thedetermined MCS index, a modulation order indicated by the determined MCSindex is QPSK.
 28. The method of claim 25, wherein a modulation orderindicated by the determined MCS index is QPSK.
 29. A terminal,comprising: a transmitter configured to transmit channel stateinformation to a base station; a receiver configured to receive downlinkcontrol information from the base station; and a controller comprisingat least one hardware processor configured to: determine a modulationorder used in a downlink data channel based on i) an MCS table having atleast one of TBS indices set to be identical to MCS indices and ii) anMCS index included in the downlink control information; and determine atransport block size (TBS) in the downlink data channel based on a TBStable including TBS indices, a TBS index indicated by the MCS indexincluded in the downlink control information and the number of physicalresource blocks (PRBs) included in the downlink control information,wherein, when the number of repetitive transmissions of the downlinkdata channel is less than or equal to a predetermined number of times, amodulation order indicated by the MCS index included in the downlinkcontrol information is one of QPSK and 16QAM; and wherein, when thenumber of repetitive transmissions of the downlink data channel exceedsa predetermined number of times, a modulation order indicated by the MCSindex included in the downlink control information is identical, each ofall TBS indices mapped from the MCS indices in the MCS table is set tohave a value identical to a corresponding MCS index.
 30. The terminal ofclaim 29, wherein: in the MCS table, (i) a range of the MCS indices isfrom 0 to 15; (ii) a range of the TBS indices is from 0 to 15; and iii)each of all TBS indices mapped from the MCS indices in the MCS table isset to have a value identical to a corresponding MCS index.
 31. Theterminal of claim 29, wherein, when a TBS index indicated by the MCSindex included in the downlink control information in the MCS table isidentical to the MCS index, a modulation order indicated by the MCSindex is QPSK.
 32. The terminal of claim 29, wherein a modulation orderindicated by the MCS index included in the downlink control informationis QPSK.